Overview

_____________________________________________________________________________________________________________

    The 1500 km long North Anatolian Fault (NAF) is one of the world’s largest active continental strike-slip faults and forms the northern margin of the Anatolian plate. The right lateral NAF has an average slip rate as measured by GPS of approximately 20 mm/yr (McClusky et al., 2000) and a record of large devastating earthquakes this century (Figure 1).

              Figure 1. Surface offsets associated with major earthquakes that ruptured the NAF this century.   

    The tectonic framework of the eastern Mediterranean is characterized by convergence of the northward moving Arabian and African plates with the relatively stable Eurasian plate. In eastern Turkey, the convergence of the Arabian and Eurasian plates since the Miocene has resulted in tectonic shortening, a topographic high (the Anatolian Plateau) and extrusion of the Anatolian plate westward during the past 5-10 Ma (Figure 2). All indications are that the NAF is a newly coalescing continental transform plate boundary. This gives us an opportunity to study a snapshot of lithospheric deformation in its evolution into plate boundary at the surface and at depth.

       Figure 2. Tectonic map of the Eastern Mediterranean region with our study area along the NAF.

    At the surface the NAF has a large arc shaped trace with sub parallel splays and a surface width from several meters to tens of kilometers. The surface trace shows up very well on the ground (Figure 3).  Despite much geological work at the surface, the deep structure of the NAF is relatively unknown.

Figure 3. Panoramic photo of NAF taken east of Eskipazar.

    We propose to study the central portion of the NAF using data from a 2-year, 40 station portable broadband seismic deployment to address the following questions:

(1) Is the NAF a lithospheric-scale transform fault and if so, how does the lithosphere respond to the deformation? Is the NAF a thin vertical fault at depth or a broad zone of deformation? Are the crust and upper mantle deformation coupled or decoupled?

(2) How does the deeper asthenospheric flow signature relate to the crustal velocity field (as defined by GPS studies) and westward tectonic escape model for the Anatolian plate?

(3) How does the spatial distribution and composition of magmatism along the fault zone in the last 10 Ma relate to the deep structure of the fault?

(4) How do the fault segments, rupture segments and major splays interact along strike and at depth? What is the depth of the seismogenic zone, and how does it relate to the segmentation defined by the major earthquakes this century?

    In order to answer the questions posed above we will use seismic tomography (teleseismic, regional and local), receiver function analysis, regional waveform modeling, surface wave dispersion, crust and mantle anisotropy measurements, gravity modeling, and seismicity studies. The deployment geometry shown in Figure 4 is designed to facilitate the wide range of studies. Our proposed activities will have a broad benefit to society because of the high earthquake hazard associated with NAF. Better characterization of the fault will enhance our understanding of continental strike-slip faults worldwide.

Figure 4. Tectonic map of the study area with station locations, volcanics and local seismicity.